Tanning agent and method of making and using same



Patented Sept. 14, 1954 UNI-TED STATES MTEN'T GFF'ICE- 2,689,163 1 1%.; .13. [.1 ital- "I11 TQ'FL'ITJ it? TANNING AGENT A D METHOD OF MAKIN AND USING SAME Mt uuis'raqiiet; Poiigues-les-Ea'iix, r sets Ndpr'av'vi'ng.;, Application ms 17, 1951, Serial .No. 221,319 Claii'n's priority; application France October 27, 1948 Th present inventi nrelates toanov l. nnins. product, the method of. manufecturin s i prod-i uct, a tanningbath in the,..preparation of which this..novel,tanning. product..is employed and a proces f tanning. .thEIW h.-... t.

The .present invention .is a. continuation-ink part of myv .copending application filed October 18, 1949 having'the' Serial,No...122,.125,

The ..use,.of,.,sol11b1e..zirconi1lm compounds as.

tanningagents is [known in Ltheprior. art. .More.

particularly, so1utions,.. contain ing. solublel, zir.conium sulfatepr chloride .saltshavebeen utilized in.

tanning baths but non-uniform and incomplete tanning results have ."been obtained. The prior. art. has. attempted to',.remedy. ...thes.e defects by...

adding a soluble sulfate bompoundtto the tanning batncontaining the; zirconium'compound to improve. the. extent of tanning It .has. also been sug ested. to add,..w,ater solublesilicicacid com: pounds orwater. soluble. silicates to thetzirconium containingtanning; liquorv in orderhto ,obtain .im.-

proved coloration of. the. hideiorskin Howeven.

a so.luble...zirconiuin. salt absorbed in av silica gel. I

This tanning agentlis. preferably. produced .jdi-r. rectly'by reactioriifriom a sodium silicowzirconate with aconcentratedniinerali acid at elevated temperatures, wherebya'scomplex water soluble zire conium'isalt istforined simultaneous with, and

imbedded in thepo'res of, "the. silica gel... This resultant product," which is.in theiorm of a pulverulent solid, .Lcan". ,bei useddirectly. in the tanning bath bythe slow dissolution of the. oomplex. zirconium sa'lt out of the pores. of the insoluble. silica gel, tofunction asthe tanning agent for the. animal skinsin thepresenciof the silica gel.. .Thus, the tanning bath is prepared by. dis.-

solving. the tanninggjagent, namely the zirconium.

salt absorbed by the silica gel,".in.water... This tanning agent. willv slowlyidissolvesothat the bath .actuailly contains not only .zirconium salts absorbed by. silica gel, but .also.'the liberated. zirconium salt.,.in. .directs01ution, in. the .water .form:. ing the base of the bath. This liberation of the zirconium salt occurs-over an extended period of time at asubstantially uniformrate v v "duringlthe ex eetn e pi ri'o'd, a substans,'the're willj 35101. durin at m g with .a" his 1 the amounts: 'solub 21% oliiiiii s. (o1. 8-94.25;

tially uniform. .concentitation .of. liberatedzirconiw. um saltensuring uniform.tanning action.., ln this relationship, .the silioaigel actsas a surface vac: tive. agent. (not as .a. tanning .agent) .to assistthe. zirconium alt in its. .afiini y orand pe tra ion... into the fibets of.. t he;Sk-in.,-.i The leather, obtained. by the instant processhis very white, very full, has anexcellent hand or feel, and a very beautiful I D B HQG-.,,, Accordingly,. an,obj ec,toitheinstant. invention. is t p videa p el andsun rmntanning. aeent,.. comprisinga complex zirconium salt absorbed in the pores ofasillcai elm. Another. bj t of...t epres ntt nv n i n isthe ve me t f 5 a process fwdirectly prod cin thisnovel tanning agent from sodium silico-zir- AL u her ob ect of, this i ve tioniis the us of these novel tanning agents in thepreparation on. a tanning bath to produce a superior quality th r 1. man" .zn tr/inf". 1.. i.. a r further ob ect otthi invention is. the. de-.. 0Pm l .Of %.-prQ9e eintannineewi h a com.. plex soluble zirconium salt embedded in a silica -Mm 1.x 1., i'i xni y, 'i 0 Ant-moi.

Fur b e ts...and-ad an a esthe pr s nt invention will be apparent from the following dec ipt n,... av esult o umydi eove the disadva ta es of t i .witha .zirc niu salti are li nat d.

a: s er or leathe remai d. y usi ia sil ca e ryiit is ap a e 1. that. t e qtid of a i ee gel is ial .physi wehem al.in a p e. 113v hes e e m 3 -i e. zi i o i 131 ..,t1 be f @due h ur. latedfa'nd 810wanni ng aqtign' is effected.) .1e

The quant ty superior results: of the chlorides, nitrates or the like. The molecular composition for the sulfate salt is represented by the following ratio, 1 mol. ZrOz for 0.8-2.2 mol. $03, the preferred range being 1 mol. ZrO-z:1.2-1.8 mol. S03. The molecular ratio for the chloride salt is 1 mol. ZrOzzLG- mol. HCl, preferably 1 mol. ZrOz:1.8-2.6 mol. HCl.

Another embodiment of the instant invention is the development of a process for producing the complex soluble zirconium salt dispersed in a silica gel directly and simply from a sodium silico-zirconate by treatment with a concentrated mineral acid at temperatures above 105 C. The sodium silico-zirconate can be economically produced from the mineral zircon, a zirconium silicate, by calcination in the presence of sodium carbonate. More specifically, the transformation of zircon into the sodium silico-zirconate (e. g. NazSiZrO) can be carried out by fritting the powdered zircon with an excess of about 5% sodium carbonate at about 1000 C. for two hours. The fritted mass containing the sodium silicozirconate, is subsequently treated with a concentrated acid, preferably sulphuric, hydrochloric, nitric acid or non-precipitating mixtures thereof, the concentration of the acid being sufiicient to raise the temperature of this exothermic reaction above 105 C. and preferably to 110-120 C. The exothermicity of this reaction vaporizes the water, resulting thereby in a substantially dry end product. The amount of acid utilized must be sufficient to transform all of the NazO and all of the acid soluble ZIOz into the water soluble salts of the specific mineral acid used. Illustratively, using H2804, the Zr02 and NazO combine with the H2804 to form a complex salt of NazSO4 and zirconium sulfate, having the molecular composition represented by the ZrOzzSOa ratio specifically set forth above.

The concentration of the acid must be such that an exothermic reaction ensues. When using sulfuric acid the concentration in relation to the water in the mass is 3560 B. which is equivalent to a specific gravity of 1.32 to 1.71 or a concentration of 41-78% by weight. A more concentrated acid, such as represented by 66 B. (93% Has-O4), is added to a paste of sodium silico-zirconate already containing water, so that a final concentration of 35-60 B. H2504 is obtained. By regulating the concentration of the acid within the above specified limits, the character of the gel and of the zirconium salt can be varied so as to render them especially suitable for obtaining varied tanning results. By maintaining the amount of acid constant, and decreasing the amount of water added to the sodium silicozirconate to form the paste, the concentration of the acid is increased and the temperature of the reaction is elevated resulting in an enlargement of the grains of silica gel and a decrease in the absorptive capacity of the gel, and in a smaller amount of combined water with the complex zirconium salt which is characterized by a slower dissolution of the zirconium salt in water. When maintaining the amount of the acid constant and increasing the amount of water added to the sodium silico-zirconate to form the paste, the concentration of the acid is decreased and the temperature is lowered, resulting in a more voluminous and absorptive silica gel composed of smaller grains, and in a greater amount of combined water with the complex salt of zirconium. Consequently, variations in the temperature of the reactions, in the concentrations of the acids, and in the ZrO22SO3 ratio modify the tanning properties of the resultant product which is a pulverulent solid of a complex salt of zirconium embedded and absorbed in a silica gel.

Hydrochloric acid may also be utilized to attack the sodium silico-zirconate, but in concentrations represented by 13-22 B., preferably 16-20 B., the broad range being equivalent to a specific gravity of 1.10-1.18 or 20-36% P161 by weight, in amounts necessary to convert the total Nazo content to NaCl and the ZrO: content into a soluble zirconium chloride salt having the molecular composition previously discussed. Similarly to the use of sulfuric acid, the concentration and quantity of HCl can be varied within the above specified limits, taking into consideration the sodium silico-zirconate to be treated and the results desired. Thus, the speed of dissolution of the zirconium compound in the tanning solution, and the physical characteris-- tics of the silica gel as to grain size and absorptive properties, can be regulated by adjusting the concentration of the acid, the temperature of the acid attack and the cooling of the reaction mass.

Nitric acid can also be used to attack the sodium silico-zirconate. However, the difference in the molecular weights of the mineral acids require different amounts and concentrations thereof to produce the desired tanning product. Accordingly, the concentration of the nitric acid lies within the range of 20 B. and 40 B., which is equivalent to a specific gravity of 1.16 to 1.38 or a weight percentage of 26 to 63% HNO3.

The desired concentrations of the acids are those which are present in the acid solutions at the time of bringing it into contact with the pulverized frit of sodium silico-zirconate. These concentrations can be obtained by either mixing the necessary amount of water with the commercial acid, or preferably by making a paste of the fritted mass with water to which a strong acid is subsequently added. In lieu of single acids, non-precipitating mixed acids such as non-precipitating mixtures of sulphuric and nitric acids, etc., may be utilized, the degree of dilution of the acids being dependent on the molecular weight of the acids used.

This economical process of producing the zirconium tanning agent in the form of a pulverulent solid which can be used directly in the tanning bath has rendered this tanning process commercially feasible. To date, in spite of the advantages 0f zirconium tanning, the high cost of the zirconium salts has prohibited its use on an industrial scale. However, the zirconium minerals are inexpensive, zircon being one of the cheapest. According to the instant process of producing the tanning agent directly from the mineral, zirconium tanning is rendered economical as well as productive of a superior leather. Although zircon is the preferred mineral, other zirconium minerals such as zirkites, baddeleyites, etc., can be utilized alone or admixed with silica or zircon. Furthermore, the instant process produces good yields of tanning agents possessing a high degree of purity.

The following examples are additionally illustrative of the process of obtaining the zirconium tanning agent of the instant invention, and are not to be construed as limiting the scope thereof.

EXAMPLE A 250 kgs. of silico-zirconate of sodium (containing substantially 2 25 kgs. of ZrOzSiO2Na2O and 5 kgs. of impurities), preferably ground to a powder corresponding to mesh, are trans- 51 formed into a paste by add-ing 210 liters of water.

Then 220 kgs. of sulfuric acid at 66 B. (i. e. 93% of pure H2804) are rapidly added to the paste with vigorous stirring.

The reaction is exothermic and the temperature increases rapidly to above 110 C. and a part of the added water is vaporized thereby. Substantially all of the silica is transformed into a voluminous gel having a great absorbing capacity which is in the form of coarse grains substantially completely insoluble in water.

The ZI'O2 and the Na20 combine with the H2SO4 in the form of a complex salt which is soluble in Water and is absorbed by the silica gel.

600 kgs. of tanning product are thereby obtained, having approximately the following analysis:

Percent Soluble ZIOz about 20 Total SiOz about NazO about 10.40 Total S03 (of which 16.4% is titratable S03) about 30 Insoluble about 3 Total water (of which about 19 parts can be eliminated only by prolonged heating at 160 to 450) about 26.60

Total 100.00

In this product the ratio ZTOQ 1S about which corresponds to a basicity of 36 on the Schorlemer scale.

The complex compound of zirconiumdissolves slowly in water, about 3 hours being necessary to obtain complete dissolution.

EXAMPLE B 245 kgs. of the ground dry sodium silicozirconate frit, are rapidly introduced into 146 kgs. of HCl as a 20 B. acid solution (5. g. 1.16, 33% I-ICl) which contains 372 grams I-ICl per liter. Thus, there are used a total of 390 liters of this acid of 1.16 s. g. equivalent to 452 kgs.

After agitating the mixture for some minutes, the reaction commences. When the temperature of the mixture has risen to about 107 C. r

the same is allowed to cool giving thereby a yellowish easily pulverizable mass which is almost dry.

After being cooled, there remains about 610 kgs. of a product having approximately the folstantially insoluble) about 9.8

Another novel feature of this invention comprises the tanning of skins or hides in a bath containing the zirconium tanning agent obtained according to the above procedure. This zirconium tanning product constitutes a water soluble complex salt of zirconium dispersed or absorbed in a voluminous silica gel, the proportion of silica per mole of ZIO2 being 0.1 to 2 moles and preferably 0.2-1.3 moles. The soluble zirconium salt dissolves slowly inthe. tanning bath, during a period of about /2 to 4 hours. due to the presence of the silica gel which coats the grains of soluble zirconium salt and remains suspended in the bath. The pH of the bath. isv between 0.5-2, preferably between 0.5-1.9 in order to maintain the zirconium salt in solution and effect tanning of the skins. At a higher pH, the zirconium salt gives colloids deteriorating the tanning properties of the bath. The desired tanning is obtained with a concentration of 10-70 gms. and preferably 25 gms. of zirconium salt, calculated as ZrOz, per liter of tanning solution. The silica is in the form of a silica gel and exerts only a physical or physico-chemical effect on the tanningbath, wherein the soluble complex zirconium salt is the effective tanning agent.

The soluble ZrOz content of the tanning bath, the SiOalZrOz molecular ratio and the pH of the bath should be the same as defined above.

The following examples are additionally illustrative of the process of tanning with the novel tanning agents of the instant invention, and are not to be construed as limiting the scope thereof.

Example I For tanning 1 kg. of pickled sheepskins (pH about 2) the following bath can be used:

Water 2,000 cc. NaCl gms. Product of the sulfuric acid attack upon sodium silico-zirconate frit, as

per Example A, at 20% ZrOz and at a Schorlemer basicity of about 40 (i. e. about 50 gms. of 2102) 250 gms.

After slowly dissolving the tanning product, thebath contains about 25 gms. of silica (SiOz) in the form of an insolubl voluminous silica gel, having absorptive capacities. The grains of said gel are such that they cannot substantially penetrate into the skin.

The skins are agitated in the bath for 3 hours; then permitted to stand overnight or in the tanning solution or on a support. Then the skins are neutralized to about a pH of 4.5 by slowly adding to the bath sodium bicarbonate, borax or any other neutralizing agent.

The skins are permitted to stand 24 hours in the vat or on the support and washed to remove solubl salts and adhering silica gel. The skins are then finished in any known manner.

The leathers obtained are very white, very full,

I have an excellent feel to'the touch and a very beautiful hair-side.

Example 2 For 1 kg. of pickled sheepskins (pH about 2) the tanning bath may be as follows:

Water 2 liters Sodium sulphate crystallized 280 grams Product of Example 13 (made with HCl) 260 grams.

7 then washed to remove silica, and finished in the usual way.

The leather is a little less white than the product of Example 1. It is well tanned, very full and has a very pleasing appearance and a good bloom.

Skins and hides other than pickled sheepskins can be tanned in accordance with the instant invention such as horse, calf, beef, cattle, etc. The type of hide used will determine the length of time of the skins sojourn in the tanning bath and the quantity of H02 fixed in the skin which is usually between 12 and 24% of the dry leather.

The invention has been described with respect to certain specified examples and preferred methods, but it will be appreciated by those skilled in the art that suitable variations and modifications of the invention may be made without departing from the principles and real spirit of the invention.

What is desired to be secured by Letters Patent 1. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles S102 per each mole of ZrO2, said bath containing -70 gms. zirconium salt calculated as ZIOz per liter.

2. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles SiOz per each mole of ZrOz, said bath containing 25 gms. zirconium salt calculated as ZrOz per liter.

3. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles $102 per each mole of ZrOz, said bath containing 10-70 gms. zirconium salt calculated as ZI'Oz per liter, the pH of said tanning bath being less than 2.

4. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles SiOz per each mole ZrOz, said bath containing 10-70 gms. zirconium salt calculated as Z1O2 per liter, the pH of said tanning bath being between 0.5-2.

5. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles 8102 per each mole of Z102, said bath containing 10-70 gms. zirconium salt calculated as ZrOz per liter, said water soluble complex of inorganic sodium zirconium salts being partly dissolved in the water of said bath and partly still distributed through and embedded in said silica gel.

6. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium sulfate salts represented by the ratio:

said bath containing 10-70 gms. zirconium salt calculated as ZrOz per liter.

7. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium sulfate salts represented by the ratio:

so 0.8 to 2.2

said bath containing 10-70 gms. zirconium salt calculated as ZrOz per liter, the pH of said tanning bath being between 0.5-2.

8. A tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially Water insoluble and having a greater than colloidal size, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium chloride salts represented by the ratio:

said bath containing 10-70 gms. zirconium salt calculated as ZrOz per liter.

9. A process of tanning skins and hides to obtain a superior quality leather, comprising the steps of treating pickled skins with an aqueous tanning bath essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble, having a, greater than colloidal size and being larger than the pores of the pickled skins, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles SiOz per each mole of ZlOz, said bath containing 10-70 gms. zirconium salt calculated as ZrOz per liter, so that said silica gel slowly releases said inorganic sodium zirconium salts into the water in contact with the skins, thereby tanning the same; allowing the skins to remain in contact with said tanning bath until the skin is thoroughly tanned; and recovering a superior quality leather.

10. A process of tanning skins and hides to obtain a superior quality leather, comprising the steps of treating pickled skins with an aqueous tanning bath having a pH of less than 2 and essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble, having a greater than colloidal size and being larger than the pores of the pickled skins, said silica gel particles having distributed therethrough and embedded therein a water soluble complex of inorganic sodium zirconium salts in the proportion of 0.1-2 moles SiOz per each mole of ZrOz, said bath containing -70 gins. zirconium salt calculated as ZlOz per liter, so that said silica gel slowly releases said. inorganic sodium zirconium salts into the water'in contact with the skins, thereby tanning the same; allowing the skins to remain. in contact with said tanning bath until the skin is thoroughly tanned; and recovering a superior quality leather.

11. A process of tanning skins and hides to obtain a superior quality leather, comprising the steps of treating pickled skins with an aqueous tanning bath having a pH between 0.5-1.9 and essentially consisting of an aqueous suspension of discrete silica gel particles being substantially water insoluble, having a greater than coll idal size and being larger than the pores of the pickled skins, said silica gel particles having distributed therethrough and embedded therein a Water soluble complex of inorgan c sodium zirconium salts in the proportion of 0.1-2 moles S192 per each mole of ZrOz, said bath containing 1 3-70 zirconium salt calculated as ZrOz per liter, so that said silica gel slowly releases said inorganic sodium zirconium salts into the water in contact with the skins, thereby tanning the same; allow-- ing the skins to remain in contact with said tanning bath until the skin is thoroughly tanned; and recovering a superior quality leather containing12-2 l% ZrOz.

12. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium salts, said water-soluble complex being distributed through and. embedded in discrete silica gel particles being substantially waterinsoluble and having in Water a particle size greater than colloidal size, the amount of silica gel per mole of ZI'Oz being 0.2-2.0 moles.

13. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium salts, said water-soluble complex being distributed through and. embedded in discrete silica gel particles being substantially waterinsoluble and having in water a particle ize greater than colloidal size, the amount of silica gel per mole of 2102 bein 0.2-1.3 moles.

14. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium sulfate salts, said water-soluble complex being distributed through and embedded in discrete silica gel particles being substantially water insoluble and having in water a particle size greater than colloidal size, the amount of silica gel per mole of Z1 02 being 0.2-2.0 moles.

15. A product useful for tanning, comprising a Water-soluble complex of inorganic sodium zirconium chloride salts, said water-soluble complex being distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, the amount of silica gel per mole of Zr02 being 0.2-2.0 moles.

16. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium sulfate salts and having a molecular composition represented by the following ratio:

said complex salt being distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, the amount of silica gel per mole of Z1O2 being 0.2-2.0 moles.

17. A product useful for tanning, comprising '10 a water-soluble complex of inorganic sodium zirconium sulfate salts and having a molecular composition represented by the following ratio:

said complex salt being distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in Water a particle size greater than colloidal size, the amount of silica gel per mole of Zr02 being 0.2-2.0 moles.

18. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium chloride salts and having a molecular composition represented by the following ratio:

said complex salt being distributed through and embedded in discrete silica gel particles being substantially Water-insoluble and having in water a particle size greater than colloidal size, the amount of silica gel per mole of mm being 0.2-2.0 moles.

19. A product useful for tanning, comprising a water-soluble complex of inorganic sodium zirconium chloride salts and having a molecular composition represented by the following ratio:

said complex salt being distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, the amount of silica gel per mole of ZrOz being 0.2-2.0 moles.

20. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with sufficient concentrated mineral acid to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid while raising the temperature 01 the reaction mass to above C., and recovering a substantially dry, pulverulent solid product composed of a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles.

21. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises calcining a silicacontaining zirconium ore with sodium carbonate to produce sodium silico-zirconate, treating said sodium silico-zirconate with suflicient concentrated mineral acid to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid while raising the temperature of the reaction mass to above 105 C., and recovering a substantially dry, pulverulent solid product composed of a water soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles.

22. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete 11 silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with sufficient concentrated sulfuric acid to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid having the molecular composition represented by the ratio:

while raising the temperature of the reaction mass to above 105 C., and recovering a substantially dry, pulverulent solid product composed of a water soluble complex of inorganic sodium zirconium sulfate salts distributed through and embedded in discrete silica gel particles.

23. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with suificient concentrated hydrochloric acid to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid having the molecular com-position represented by the ratio:

HC1-O.64

while raising the temperature of the reaction mass to above 105 C., and recovering a substantially dry, pulverulent solid product composed of a water soluble complex of inorganic sodium zirconium chloride salts distributed through and embedded in discrete silica gel particles.

24. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with suflicient concentrated sulfuric acid having a concentration between 35-60 B. to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid having the molecular composition represented by the ratio:

while raising the temperature of the reaction mass to above 105 C., and recovering a substantially dry, pulverulent solid product composed of a. water-soluble complex of inorganic sodium zirconium sulfate salts distributed through and embedded in discrete silica gel particles.

25. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with sufiicient concentrated hydrochloric acid having a concentration between l3-22 B. to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid having the molecular composition represented by the ratio:

rm 1 H01 O.6-4

while raising the temperature of the reaction mass to above C., and recovering a substantially dry, pulverulent solid product composed of a water soluble complex of inorganic sodium zirconium chloride salts distributed through and embedded in discrete silica gel particles.

26. A process of obtaining a water-soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles being substantially water-insoluble and having in water a particle size greater than colloidal size, which comprises treating sodium silico-zirconate with sufficient concentrated concentrated mineral acid to convert all of the sodium and zirconium into their water-soluble salts of the mineral acid while raising the temperature of the reaction mass to about -120 C., and recovering a substantially dry, pulverulent solid product composed of a water soluble complex of inorganic sodium zirconium salts distributed through and embedded in discrete silica gel particles.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,127,304 Mauthe et a1 Aug. 16, 1938 2,395,472 Fernald Feb. 26, 1949 2,477,638 Milliken et a1. Aug. 2, 1949 2,481,493 Blue Sept. 13, 1949 FOREIGN PATENTS Number Country Date 917,317 France Sept. 6, 1946 

1. A TANNING BATH ESSENTIALLY CONSISTING OF AN AQUEOUS SUSPENSION OF DISCRETE SILICA GEL PARTICLES BEING SUBSTANTIALLY WATER INSOLUBLE AND HAVING A GREATER THAN COLLOIDAL SIZE, SAID SILICA GEL PARTICLES HAVING DISTRIBUTED THERETHROUGH AND EMBEDDED THEREIN A WATER SOLUBLE COMPLEX OF INORGANIC SODIUM ZIRCONIUM SALTS IN THE PROPORTION OF 0.1-2 MOLES SIO2 PER EACH MOLE OF ZRO2, SAID BATH CONTAINING 10-70 GMS. ZIRCONIUM SALT CALCULATED AS ZRO2 PER LITER. 